Identification and characterization of intestinal Clostridium spp. and Lactobacillus spp

Human gastro-intestinal tract harbors hundreds of bacteria species. These complex microflora play an important role in the host health and disease. Even though the composition, metabolism and regulatory mechanisms of the flora have been in the research focus since the 1970's, with the complexity of the system and limited research tools, there are still many unknowns and many hypothesizes needed to provide scientific evidences for their role in the intestine.; The objectives of this thesis were to determine if (1) SFP (Shahidi-Ferguson perfringens) medium supports the growth of Clostridium perfringens exclusively; (2) probiotic consumption changes the fecal lactobacilli composition; and (3) the delivery vehicles for Lactobacillus acidophilus NCFMRTM would influence the human fecal microbiota.; The SFP medium was originally developed in the 1970's for enumeration and identification of C. perfringens. It is still commonly used for selective counting of C. perfringens from various samples. When comparing the results of this selective culture method with molecular methods (PCR and sequencing), the majority of the colonies formed on the selective medium were clostridia but not C. perfringens. It shows the necessity of continuous validation of the selective agent as well as the phenotypic reference library.; It is believed that probiotic consumption could bring health benefits to the host. But a challenge is to differentiate the exogenous probiotic strain from the indigenous intestinal microflora. Combining the molecular techniques with traditional culture method enabled the speciation of the lactobacilli colonies on Rogosa SL medium. It was shown that the fecal lactobacilli profiles changed significantly before, during and after probiotic consumption.; It was hypothesized that dairy products are preferred delivery vehicles for probiotics. However, by comparing milk versus water as delivery vehicles for L. acidophilus NCFMRTM, the results did not provide a scientific proof for the hypothesis. In addition, the exogenous L. acidophilus NCFMRTM did not affect the populations of other endogenous genera of bacteria.; With the continuous adoptation of newly developed molecular techniques into microbial community analysis, the polymorphic approaches will eventually lead to the ultimate goal of the intestinal microflora research---understanding the role of intestinal microflora in host health and diseases.